Add explicit Release configuration to standalone.gypi to appease Xcode.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/12225043

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13602 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

build/standalone.gypi

@@ -87,6 +87,9 @@
       'Debug': {
         'cflags': [ '-g', '-O0' ],
       },
+      'Release': {
+        # Xcode insists on this empty entry.
+      },
     },
   },
   'conditions': [